Photographic process comprising dye bleaching step



United States Patent U.S. Cl. 9648 24 Claims ABSTRACT OF THE DISCLOSURE An improved photographic process comprising an improved and rapid dye bleaching step comprises: (1) exposing to an image pattern of activating radiation a dyesensitized photosensitive copy medium which becomes activated at portions thereof which are exposed to such activating radiation and, (2) applying to the exposed medium a dye bleaching solution of a thionate selected from at least one of the group of sulfites and bisulfites, and especially those of Groups I-A and II-A metals, said thionate having a concentration of a least about 0.5 mole of thionate per liter of solution. This dye bleaching solution can be applied to the photosensitive copy medium along with the image-forming material, stabilizing bath, fixing bath and/ or stop bath. In a preferred embodiment, the dye bleaching solution is combined with the fixing bath. In such an embodiment wherein the thionate is potassium sulfite and the fixing bath is an aqueous solution of sodium thiosulfate, the potassium sulfite serves the dual function of a bleaching agent for a colored dyesensitive copy medium and also a preservative for the sodium thiosulfate.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the field of photographic reproduction systems, and, more specifically, to a photo graphic system utilizing an improved copy medium comprising a photosensitive material sensitized with a bleachable dye, which photosensitive material when activated by suitable means, is capable of producing a visible image.

Description of the prior art 'Data or image storage media comprising radiationsensitive materials such as titanium dioxide are described in detail in U.S. Pats. 3,152,903; 3,152,904; 3,052,541; French Pats. 345,206 and 1,245,215 and in commonlyowned co-pending U.S. application Ser. No. 199,211, now abandoned, filed May 14, 1962 in the names of Elliot Berman et al. In the aforementioned U.S. patent application, radiation-sensitive titanium dioxide functions as a photosensitive component of the media and exposure of said media to activating means such as radiant energy, electron beams or the like results in the storage of a reversible latent image pattern therein. The reversible latent image pattern exists for a limited time during which said pattern can be converted to an irreversible form and read out visually by contacting said pattern with a suitable image forming material, such as a chemical redox system. In the aforesaid U .S. and French patents, the radiation-sensitive material'is combined with at least one component of an image-forming material prior to exposure to activating means. For example, U.S. Pat. 3,152,904

describes a photosensitive copy media comprising photosensitive materials such as titanium dioxide in combination with a reducible metal ion such as silver nitrate. This copy media is exposed to activating means to produce a visible image. On the other hand, U.S. Pat. 3,152,903 discloses a system wherein the photosensitive material is used in combination with both an oxidizing agent such as silver nitrate and a reducing agent such as hydroquinone. Upon exposure to suitable activating means, a visible image is formed.

One of the features of the above-mentioned data or image storage systems is that the photosensitive materials are often sensitive to a very narrow range of electromagnetic radiation. Therefore, it is often desirable to sensitize these photosensitive materials to additional ranges of electromagnetic radiation by application of dyes. Such dyes are well knoWn to the art and include, for example, cyanine dyes, dicarbocyanine dyes, the carbocyanine dyes, and the hemicyanine dyes. Such dye-sensitized systems are disclosed in co-pending application U.S. Ser. No. 432,887, now abandoned, filed Feb. 15, 1965, in the names of E. Berman et al., co-pending application U.S. Ser. No. 359,956 filed Apr. 15, 1964 in the names of R. F. Bartlett et al., now U.S. Pat. No. 3,414,410 and copending application U.S. Ser. .No. 633,689 filed Apr. 26, 1967 in the names of J. Keller and R. Sprague.

One of the problems with using such dyes to sensitize the photosensitive medium is the removal of the dye after development of the latent image to a visible image in order to obtain a final print with a white background. In the past this dye removal has been accomplished by dissolving the dye out of the substrate or by contacting with a suitable oxidizing agent. However, these methods have either been extremely slow or the oxidizing agent has been so strong that it produced detrimental effects upon the visible image formed in the final print.

SUMMARY OF THE INVENTION It has now been unexpectedly found that a photosensitive medium sensitized with a bleachable dye in the colored form may be rapidly converted to the colorless state without detrimental effects to the final print when contacted with a solution of a thionate selected fromat least one of the group of the sulfites and bisulfites, and especially those thionates of the metals of Groups I-A and IIA of the Periodic Table, preferably having a concentration of from about 0.5 mole of thionate per liter of solution to a solution being saturated with the thionate. More particularly, this invention involves a process for recording an image pattern of activating radiation comprising exposing to an image pattern of activating radiation a photosensitive copy medium sensitized with a bleachable colored dye which becomes activated at portions thereof which are exposed to activating radiation, wherein the improvement comprises applying to the exposed copy medium a solution of a thionate such as the sulfites and bisulfites of the Groups I-A and II-A metals, wherein the concentration is as above described. In a preferred process, the thionate is incorporated in image-forming material, in stabilizing bath, in fixing bath and/or in stop bath which is applied to an exposed and developed photosensitive copy medium. Therefore, a preferred embodiment comprises a photosensitive copy medium sensitized with a bleachable dye which is exposed to an image pattern of activating radiation, then Periodic table from Langes Handbook of Chemistry, 9th edition, pp. 56-57.

contacted with an oxidizing agent such as a solution of silver nitrate, then contacted with a solution of a reducing agent such as Metol, and finally contacted with a fixing bath and combined dye-bleaching solution comprising, for example, sodium or ammonium thiosulfate, and potassium sulfite, wherein the concentration of the potassium sulfite is in a concentration from at least about 0.5 mole of sulfite per liter of solution up to a solution saturated with sulfite.

DESCRIPTION OF PREFERRED EMBODIMENT(S) The photoconductor or photocatalyst preferred in this invention are metal containing photoconductors. A preferred group of such photosensitive materials are the inorganic materials such as compounds of a metal and a non-metallic element of Group VI-A of the periodic table such as oxides, such as zinc oxide, titanium dioxide, zirconium dioxide, germanium dioxide, indium trioxde; metal sulfides such as cadmium sulfide (CdS), zinc sulfide (ZnS) and tin disulfide (SnS metal selenides such as cadmium selenide (CdSe). Metal oxides are especially preferred photoconductors of this group. Titanium dioxide is a preferred metal oxide because of its unexpectedly good results. Titanium dioxide having an average particle size less than about 250 millimicrons and which has been treated in an oxidizing atmosphere at a temperature between about 200 C. and 950 C. for from about 0.5 hour to about 30 hours is especially preferred, and more especially that titanium dioxide produced by high temperature pyrolysis of titanium halide.

Also useful in this invention as photoconductors are certain fluorescent materials. Such materials include, for example, compounds such as silver activated zinc sulfide, zinc activated zinc oxide, manganese activated zinc phosphate Zn (PO an admixture of copper sulfide, antimony sulfide (SbS) and magnesium oxide (MgO), and cadmium borate.

While the exact mechanism by which this invention works is not known, it is believed that exposure of photoconductors or photocatalysts of this invention to activating means causes an electron or electrons to be transferred from the valence band of the photoconductor or photocatalyst to the conductant band of the same or at least to some similar excited state whereby the electron is loosely held, thereby changing the photoconductor from an inactive form to an active form. If the active form of the photoconductor or photocatalyst is in the presence of an electron accepting compound a transfer of electrons will take place between the photographic and the electron accepting compound, thereby reducing the electron accepting compound. Therefore a simple test which may be used to determine whether or not materials have a photoconductor or photocatalytic elfect is to mix the material in question with an aqueous solution of silver nitrate. Little, if any, reaction should take place in the absence of light. The mixture is then subjected to light. At the same time that a control sample of an aqueous solution of silver nitrate alone is subjected to light, such as ultraviolet light. If the mixture drakens faster than the silver nitrate alone, the material is a photoconductor or photocatalyst.

It is evident that the gap between the valence and the conducting band of a compound determines the energy needed to make electron transitions. The more energy needed, the higher the frequency to which the photoconductor will respond. It is known to the art that it is possible to reduce the band-gap for these compounds by adding a foreign compound as an activator which either by virtue of its atomic dimensions or by possessing a particular electronic forbidden zone structure or through the presence of traps as donor levels in the intermediate zone between the valence and the conduction band stresses the electronic configuration of the photoconductive compound, thereby reducing its band-gap and thus increasing its ability to release electrons to its conduction band. Phosphors almost necessarily imply the presence of such activating substances. The effect of such impurities may be such as to confer photoconductivity upon a compound which intrinsically is non-photoconductive. The (Ca-Sr)S phosphors are believed to be an example of this gorup. On the other hand, excessive impurity content can interfere with a compound acting as a photoconductor, as above described.

Bleachable dyes useful for sensitizing the photosensitive copy medium of this invention include, for example, the cyanine dyes, the dicarbocyanine dyes, the carbocyanine dyes, and the hemicyanine dyes. Suitable cyanine dyes are the following:

3,3'-diethyl-4,5,4',S-dibenzothiacyanine chloride; 3-fl-carboxy-ethyl-l-ethyl-6-methoxy-5-phenyl-thia-2'- cyanine iodide; 3,3-diethyl-4,5,4',5'-dibenzoxacyanine iodide; 3,3-diethylthiazolinocarbocyanine iodide; 3,3'-diethyloxacarbocyanine iodide; and 3,3'-diethyl-9-methyloxaselenacarbocyanine iodide.

Suitable dicarbocyanine dyes are the following:

3,3'-di-fi-hydroxyethylthiadicarbocyanine bromide; anhydro-3,3'-di-fi-carboxyethylthiadicarbocyanine hydroxide; 3,3'-diethyloxathiadicarbocyanine iodide; 3,3-diethyl-4,5,4',5'-dibenzothiadicarbocyanine iodide; 3'-carboxymethyl-3-ethyloxathiadicarbocyanine iodide; 3-carboxymethyl-3-ethyloxathiadicarbocyanine iodide;

and 3,3-di(carboxymethyl)oxathiadicarbocyanine bromide.

Suitable carbocyanine dyes are the following: 3,3'-diethyl-9-methyl-4,5,4,5-dibenzothiacarbocyanine chloride; anhydro-3,3'-di-fl-carboxyethyl-5,5'-dichloro-9-ethylthiacarbocyanine hydroxide; anhydro-3-{3-carboxyethyl-5,5-dichloro-9-ethyl-3-B-sulfoethylthiacarbocyanine hydroxide; 9-ethyl-3,3-di-fl-hydroxyethylthiacarbocyanine iodide.

Suitable hemicyanine dyes are the following:

Z-p-dimethylaminostyryl-4-methylthiazole methochloride;

2-[4-(p-dimethylaminophenyl)-l,3-butadienyl]-l,3,3-trimethylpseudoindolium chloride;

Z-(p-dimethylaminostyryl)-benzimidazole methochloride;

2-(p-dimethylaminostyryl)-6-ethoxy-quinoline methochloride;

6-dimethylamino-2- (p-dimethylamino-styryl) -quinoline methochloride;

Z-p-dimethylaminophenyl-6-methylbenzothiazole methochloride (thioflavine T); 3,3-dimethyl-2[6(p-dimethylarnino-phenyl)-l,3,5-hexatrienyl]indolenine ethiodide;

2 (p-dimethylaminostyryl) -3 ,5 -dimethyl-thiadiazolium nitrate;

2-p-dimethylaminostyryl-4-methylthiazole-fl-hydroxyetho-chloride; and

2-p-dimethylamino-styryl-S-methyl-l,3,4-thiadiazole-flhydroxy-etho-chloride.

Aminostyryl hemicyanine dyes are an especially preferred class of dyes because of the improved photographic exposure speed and improved image densities for a given speed achieved with photosensitive copy media so sensitized.

Additional dyes which are useful for sensitizing the photosensitive medium of this invention are the cyanine dyes described on pages 371-429 in The Theory of Photographic Process by C. E. Kenneth Mees published by McMillan Company in 1952. Other useful dyes include those known to the art as triphenylmethane dyes such as crystal violet and basic Fuchsin, diphenylmethane dyes such as Auramine O, and Xanthene dyes such as Rhodamine B.

The dyes useful in this invention may be used in solution to treat the photosensitive materials prior to their incorporation into a copy medium. These dyed photosen sitive materials can then be deposited on a substrate, or incorporated into a substrate such as a fibrous web of paper. Alternatively, the dye can be combined with the photoconductive materials in the copy medium, as per example, by dispersion of the dye in the binder for the photosensitive material. In addition, it is possible to dip dye the photosensitive substrate by merely immersing a substrate containing the photosensitive material into a solution of the particular dye.

Irradiation sources which are useful in this invention includes any activating electromagnetic radiation. Thus actinic light, X-rays, or gamma rays are effective in exciting the photocatalysts. Beams of electrons and other like particles may also be used in the place of the ordinary forms of electromagnetic radiation for forming an image according to this invention. These various activating means are designated by the term activating radiation.

The inert carrier sheet upon which the photoconductor and dyes of this invention are deposited comprises any suitable backing of sufi'icient strength and durability to satisfactorily serve as a reproduction carrier. The carrier sheet may be in any form such as, for example, sheets, ribbons, rolls, etc. This sheet may be made of any suitable materials such as wood, rag content paper, pulp paper, plastics such as, for example, polyethylene terephthalate (Mylar) and cellulose-acetate, cloth, metallic foil and glass. The preferred form of the carrier sheet is a thin sheet which is flexible and durable.

It is also useful to use a binder agent to bind the bleachable dye useful in this invention and photosensitive materials to the carrier sheet. In general, these binders are translucent or transparent so as to interfere with transmission of light therethrough. Preferred binder materials are hydrophilic or hydrophobic organic materials such as resins. Examples of suitable resins are butadiene-styrene copolymer, poly(alkyl acrylates) such as poly-(methyl methacrylate), polyamides, polyvinyl acetate, polyvinyl alcohol and polyvinylpyrrolidone.

The photoconductor should be conditioned in the dark before exposure. Such conditioning is generally conducted from one to twenty-four hours. After conditioning, the photoconductor is not exposed to light prior to its exposure to activating radiation for recording an image pattern.

The period of exposure will depend upon the intensity of the light source, particular photoconductor, the type and amount of catalyst, if any, and like factors known to the art. In general, however, the exposure may vary from about 0.001 second to several minutes.

Image-forming materials which are useful in this invention are those such as described in US. Pat. 3,152,903 and in copending application Ser. No. 199,211. These image-forming materials include preferably an oxidizing agent and a reducing agent. Such image-forming materials are often referred to in the art as physical developers. The oxidizing agent is generally the image-forming component of the image-forming material. However, this is not necessarily true. Either organic or inorganic oxidizing agents may be employed as the oxidizing component of the image-forming material. Preferred oxidizing agents comprise the reducible metal ions having at least the oxidizing power of cupric ion and include such metal ions as A+, Hg, Pb, Au+ Pt, Ni+ Sn+ Pb, Cll' and Cu Other suitable oxidizing agents useful in this invention as components of an image-forming material are permanganate (M1'104 ion, various leuco dye materials such as disclosed in co-pending application Ser. No. 623,534 filed Mar. 19, 1967 in the name of L. Case, and the like. Organic oxidizing agents include tetrazolium salts, such as tetrazolium blue and red, and diphenyl carbazone, and genarcyl red 6B (methine dye).

The reducing agent component of the image-forming materials of this invention are compounds such as the oxalates, formates, substituted and unsubstituted hydroxylamine, and substituted and unsubstituted hydrazine, ascorbic acid, aminophenols, and the dihydric phenols. Also, polyvinylpyrrolidone, alkali and alkaline earth metal oxalates and formates are useful as reducing agents. Suitable reducing compounds include hydroquinone or derivatives thereof, 0- and p-aminophenol, p-methylaminophenol sulfate, p-hydroxyphenyl glycine, oand p-phenylene diamine, 1-phenyl-3-pyrazolidone.

Additionally, the image-forming materials or physical developers may contain organic acids which can react with metal ions to form complex metal anions. Further, the developers may contain other complexing agents and the like to improve image formation and other properties found to be desirable in this art.

The thionates of the dye-bleaching solution of this invention are preferably selected from at least one of the solvent soluble sulfites and bisulfites and more especially those of the Groups I-A and IIA metals. Ammonium sulfite and bisulfite are also suitable for this invention. Potassium sulfite and bisulfite are especially preferred because of their increased solubility in an aqueous solution. Water is a preferred solvent because of its economy. However, any suitable solvent which does not significantly interfere with the reaction may be used.

The thionates of this invention may be incorporated in any of the image-forming materials or in the stop bath. The stop bath used to fix or stop the developed print are those fixing and stop baths such as described in the silver halide photographic arts. Suitably, the fixing baths contain a material which complexes excess metal ion which may be present on the developed and amplified image areas as well as the non-image areas, and prevents its further deposition as free metal. When silver ion is present, for example, water-soluble thiosulfates such as potassium thiosulfate or sodium thiosulfate are usually used as complexing agents in the fixing bath.

The invention above described is exemplified as follows:

EXAMPLE 1 A mixture of 4 parts by weight of titanium dioxide and 1 part by weight of an emulsion of poly(vinyl alcohol) resin containing about 50 percent of solids in water is used to coat paper sheets.

A sheet of the coated paper is sensitized by dipping into a solution containing 20 milligrams of Z-p-dimethylaminostyryl-4-methylthiazole metho chloride in 200 ml. of methanol, and then dried.

The sensitized paper is exposed for about twenty seconds to an image pattern of activating radiation by means of a tungsten filament light source.

The exposed prints are then dipped in a saturated solution of silver nitrate in methanol, and then in a solution comprising 5 gm. of phenidone, 40 gm. of citric acid monohydrate, and 1 liter of methanol. A visible negative image of the positive exposure image is obtained. The visible image bearing print is then immersed for about one-half second in a combined aqueous fixing and bleaching solution of sodium thiosulfate and potassium sulfite and finally washed in running Water. The fixing and bleaching solution is of the following composition:

Potassium sulfite (K -300 grams Sodium thiosulfate (Na S O -5H O):8020O grams Dispersing agent: 1 milliliter Water sutlicient to make up one liter of total solution. The print is then placed in the air to dry. The color from the print is substantially removed after about three minutes. A second sample processed as described above and which is dried by heating after the washing step loses its color and is substantially bleached after about 25-30 seconds.

The potassium sulfite incorporated in the fixing solution has the added advantage of acting as a preservative of the thiosulfate.

When the dye bleaching thionate is incorporated in a 7 thiosulfate fixing solution, it appears that from about 0.6 to 2 moles of thionate to about 1 mole of thiosulfate is the preferred range.

EXAMPLE 2 A photosensitive copy medium comprising a paper support coated with a finely-divided titanium dioxide dispersed in a polyvinyl alcohol binder which has been dyesensitized with 2-p-dimethylaminostyryl-4-methy1 thiozole metho chloride is exposed to an image pattern from a tungsten light source for 1-2 seconds duration, thereby giving an exposure of 400 meter candle seconds.

The thus-exposed copy medium is then immersed 0.1 to 0.75 second in an aqueous solution of 0.32 molar silver nitrate, then immersed 0.5 to 1.75 second in an aqueous developing solution comprising Metol (p-rnethylaminophenol sulfate), then immersed 0.8 to 2.0 seconds in a combined dye-bleaching and fixer-stabilizer bath of the following composition.

Potassium sulfite (K 50 200 grams Sodium thiosulfate (Na S O -5H O): 200 grams Glacial acetic acid: 23 milliliters Dilute to 1 liter with water The copy medium is then allowed to sit for seven minutes and then tested on a MacBeth densitometer read through a blue filter to determine the completeness of bleaching. The densitometer reading gives a relative measure of the completeness of bleaching. The more complete the bleaching, the lower the optical density will be. After seven minutes the above-tested copy medium was substantially completely bleached, being converted from a bright orange to white in the non-image areas of the copy medium. The image areas of the copy medium were not adversely affected by the bleaching process. Seven minutes after removal of the copy medium from the bleach-fixer bath the densitometer reading of the above-mentioned copy medium was 0.15.

EXAMPLE 3 A dye-sensitized TiO -coated copy medium of the composition described in Example 2 is exposed and treated as in Example 2 except that the combined dye-bleaching and fixing-stabilization bath is of the following composition:

Sodium sulfite (Na SO 150 grams Sodium thiosulfate (Na S O -5H O): 200 grams Acetic acid: 12 milliliters The optical density of the copy medium is 0.29 when measured seven (7) minutes after contacting the copy medium with the bleaching solution.

It is understood that this invention also includes the dye-bleached copy medium which comprises (1) a photosensitive compound which upon exposure to a pattern of activating radiation becomes reversibly activated in at least the radiation-struck areas, and (2) the colorless reaction product of (a) a dye and (b) a thionate selected from at least one of the group of solvent soluble sulfites and bisulfites.

We claim:

1. In a process for recording an image pattern of activating radiation comprising exposing to an image pattern of activating radiation a dye-sensitized photosensitive copy medium which becomes activated at portions thereof which are exposed to activating radiation, the improvement comprising bleaching out the dye by applying to said medium at a point in time subsequent to the exposing step a solution of a thionate selected from at least one of the group of solvent soluble sulfites and bisulfites having a concentration of at least about 0.5 mole of thionate per liter of solution.

2. A process as in claim 1 wherein the thionate is a thionate of Group IA and Group IIA metals.

3. A process as in claim 1 wherein the thionate is potassium sulfite.

4. A process as in claim 3 wherein the thionate solution is an aqueous solution of potassium sulfite.

5. A process as in claim 1 wherein the dye used to dyesensitize the photosensitive copy medium is at least one of the group selected from (1) cyanine dyes, (2) dicarbocyanine dyes, (3) carbocyanine dyes, and (4) hemicyanine dyes.

6. A process as in claim 5 which comprises subsequent to the step of contacting with a thionate solution additionally heating the copy medium in order to accelerate the dye bleaching.

7. A process as in claim 5 wherein the dye sensitizing composition is Z-p-dimethylaminostyryl-4-methylthiazole metho chloride.

8. A process as in claim 5 wherein the dye sensitizing composition is 2-p-dimethylaminostyryl-3,S-dimethyl-thiadiazolium nitrate.

9. In a process for recording an image pattern of activating radiation comprising exposing to an image pattern of activating radiation of photosensitive copy medium which has been sensitized by a dye selected from at least one of the group comprising (1) cyanine dyes, (2) dicarbocyanine dyes, (3) carbocyanine dyes, and (4) hemicyanine dyes, which becomes activated at portions thereof which are exposed to activating radiation, contacting said exposed medium with an image-forming material to produce a visible image and then fixing said visible image by contacting the medium with a fixing bath, the improvement comprising applying to said medium at a point in time subsequent to the exposing step, a solution of a thionate selected from at least one of the group of soluble sulfites and bisulfites having a concentration of at least about 0.5 mole of thionate per liter of solution.

10. A process as in claim 9 wherein the sulfites and bisulfites are those of the Group IA and Group II-A metals.

11. A process as in claim 9 wherein the thionate is a sulfite which is incorporated in the fixing bath.

12. A process as in claim 11 wherein the sulfite is potassium sulfite and the fixing bath comprises a thiosulfate solution.

13. A process as in claim 12 wherein the solvent is water.

14. A process as in claim 12 which comprises subsequent to the fixing step the additional step of heating the copy medium.

15. A process as in claim 9 wherein the dye sensitizing composition is Z-p-dimethylaminostyryl-4-methylthiazole metho chloride.

16. A process as in claim 9 wherein the dye sensitizing composition is Z-p-methylaminostyryl-3,S-dimethyl-thiadiazolium nitrate.

17. A process as in claim 9 wherein the photosensitive copy medium comprises a binder selected from at least one of the group of hydrophilic and hydrophobic binders.

18. A process as in claim 17 wherein the binder is a polyvinyl alcohol binder and wherein the binder and photosensitive material are coated on a flexible substrate.

19. A process as in claim 9 wherein the photosensitive copy medium comprises a titanium dioxide coated substrate.

20. A dye-bleached copy medium comprising (1) a photosensitive compound which becomes reversibly activated upon exposure to a pattern of activating radiation and (2) the colorless reaction product of (a) a sensitizing dye and (b) a thionate selected from at least one of the group of solvent soluble sulfite and bisulfites.

21. A copy medium as in claim 20 wherein the dye is selected from at least one of the group of (l) cyanine dyes, (2) dicarbocyanine dyes, (3) carbocyanine dyes, and (4) hemicyanine dyes.

22. A copy medium as in claim 21 wherein the dye is 2 p dimethylaminostyryl 3,5 dimethyl-thiadiazoliurn nitrate.

23. A copy medium as in claim 22 wherein the thionate Mason, L. F. A.: Photographic Processing Chemistry, is potassium sulfite. 1966, p. 34

41 copy in.claim. wherein the photo' Morgan and Morgan: Photolilo Index, Quarterly Supsensltive compound is tltamum dlOXlde. plement NO. 118, 1968, pp 6 07 References Cited NORMAN G. TORCHIN, Primary Examiner p. Cilfie, L. P.. Photography. Theory and Practice, 1937, A. T SURO PICO Assistant Examiner Langford, Michael 1.: Basic Photography, 1965, pp. US. Cl. X.R. 299-305. 10 96102 

